I. Technical Field
The present invention relates to a lead-free solder material (or soldering material), an electronic component assembly (or electronic component-connected article) using such solder material, and a process for producing an electronic component assembly.
In the present specification, for the purpose of explaining a metal composition of a solder material, a numeral or a numeral range is shown in some cases just prior to a metal element other than Sn, which means as used in the technical field of the art that the numeral or the numeral range denotes a weight percentage (% by weight) of each metal element in the metal composition and a remainder is composed of Sn.
II. Description of Related Art
In order to mounting an electronic component on a substrate, a connection by soldering is generally used as it attains superior electric connection and contributes to high productivity and workability.
As a solder material, an Sn—Pb eutectic solder has been used conventionally. However, as alternatives to the Sn—Pb eutectic solder, various lead-free solders are considered for introduction and put into practical use.
At present, as a lead-free material, Sn-0.7Cu, Sn-3.0Ag-0.5Cu, Sn-3.5Ag-0.5Bi-8.0In and so on are generally used (for example, see JP 3040929 B). These lead-free materials are reported as having a connection reliability equivalent to that of the Sn—Pb eutectic solder, and even after a heat cycle test, for example, between −40° C. and 85° C. with 1,000 cycles, they are able to show a connection quality of no occurrence of connection failure which would cause a function of a product to stop.
Another lead-free solder is proposed which is made from an Sn—Ag—In—Bi based solder added with at least one selected from the group consisting of Sb, Zn, Ni, Ga, Ge and Cu (see JP 2004-188453 A). More specifically, Patent Citation 2 discloses a lead-free solder comprising 0.5-5% by weight of Ag, 0.5-20% by weight of In, 0.1-3% by weight of Bi, 3% by weight or less of at least one selected from the group consisting of Sb, Zn, Ni, Ga, Ge and Cu, and a remainder of Sn. In examples thereof, it is described that no deformation was observed for a solder alloy even after a heat cycle test between −40° C. and 125° C. with 1,000 to 2,000 cycles.
Patent Citation 1: JP 3040929 B
Patent Citation 2: JP 2004-188453 A